Seedling Adaptability Of Populations In Pinus Densata And Its Parental Species In High Altitude Habitat

Pinus densata initial from natural hybridization between P. tabuliformis and P. yunnanensis has been identified by many genetic molecular studies. There are distinct niche divergence between the hybrid pine and its parent species. However, there were no experiments of three species in high-elevation niche for proving the variation of fitness bewteen them untill now. We had set two field experiments in high-elevation niche within cental distribution ragion of Pinus densata,24 populations from the three species were involved, to test the fitness and growth of seedlings for understanding whether P. densata is more suitable growing in this ecology niche than its parent species.The results showed that:the most of seed germination, fitness and seedling traits were significantly variation between species and between populations within species, and the large amount of variance component were identified among species or among populations. The survival rate in Oct and the rate of bud-set in Oct were the best indicators of among-species divergence. The germination rate, the rate of bud-set in Oct and the annual survival rate were the best indicators of among-populations divergence.The hybrid pine, P. densata appeared to be intermediate between P. tabuliformis and P. yunnanensis in most of traits in the early stage. Comparing to P. yunnanensis, P. densata has higher germination rate and survival rate, which suggested that P. densata could compete out P. yunnanensis by occupation of much more field resources through generating more individuals in short time. Comparing to P. tabuliformis, the hybrid pine was lower in germination rate and survival rate, but late bud-set date awarding P. densata a longer growing season, and also the secondary growth and higher seeding height were found in P. densata, suggesting P. densata could compete out P. tabulifomis by occupation of much more light resources by higher rate of height growing. The hybrid pine, P. densata, expressed transgression in 5 traits of seedling height, the crown height, the ratios of the red seedlings, the purple seedlings and seedlings of secondary growth, which would reflect its unique adaptation in the high-elevation niche.The one-year old seedling of P. Yunnanensis became yellow after winter, but began growing from the epicotyl site.In the high-elevation habitat, the parent populations with higher genetic diversity which located in the eastern edge of the Tibetan plateau had higher germination and survival rate than the other. That could be related to the unique genetic composition of them.The germination rate and bud-set time among populations of P. yunnanensis were similar in two years. The survival rate and bud-set time among populations of P. tabuliformis were similar in two years. The populations which located in high-elevation habitat and to the north had earlier bud-set time. P. tabuliformis were the highest in rates of bud-set and seedling survival, indicating its adaptive potential in high-elevation niche. P. yunnanensis was lowest in bud-set ratio in the end of growing season and survivalship, evidenced its lowest fitness in high-elevation niche of the hybrid pine. P. densata had a longer growing season than P. tabuliformis, and stronger adaptation than P. yunnanensis. That could be one of the reasons about P. densata which became a hybrid in the high-elvation habitat. Our results provide a set primary data for studies focusing on origin of high-elevation adaptation of P. densata in Tibetan Plateau.